Seasonal fluctuation of zooplankton populations in lower Delaware Bay

✍ Scribed by Don Maurer; Les Watling; Rose Lambert; Ann Pembroke

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 681 KB
• Volume: 61
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00018746

✦ Synopsis

Quantitative zooplankton samples were obtained monthly or bimonthly 15 times from June 1974 to May 1975 at three stations in lower Delaware Bay . Two 12-hour cruises were also conducted at one of the stations .

Arthropods dominated the samples in terms of number of species and number of individuals . The number of zooplankton from surface samples ranged from 58/m 3 in August to 21,092/ m 3 in June, while bottom samples varied from 259/m3 in August to 30,395/m3 in October . In general, larger concentrations of individuals were found in bottom samples .

Only on three occasions did meroplankton exceed the holoplankton, and these occurred at the shallow water stations . Meroplankton comprised a larger percentage of the bottom samples than surface samples . Zoeae of Neopanope sayi and Uca sp . contributed mainly to the large proportion of meroplankton in July 1974, veligers of Mytilus edulis in January 1975, and nauplii of Balanus s p . in May 1975 .

Copepods were the largest component of the population throughout most of the year. At all stations and depths, Arctica tonsa dominated most of the summer samples . In the spring of 1975, A . tonsa was replaced by Centropages hamatus, Temora longicornis, and Pseudocalanus minutus .

During the 12-hour cruises there were higher numbers of individuals in the bottom waters in the day with migration to surface waters in the afternoon and evening . Based on cluster analysis, five time-related assemblages were discerned : June, July-August, September-November, December, January-May . Comparison of Delaware Bay zooplankton with other estuarine systems indicated that the densities obtained locally were most similar to those reported in the York River, Virginia .